High Bridge Pottery Posted January 14, 2014 Report Share Posted January 14, 2014 Is there any way I can calculate this for the clay I use. I have seen something on glazes about working it out based on oxides which I would like to do but there is no point if I don't know what my clay is to start with. Any info on COE for clay and glazes will be very much appreciated. Thank you Link to comment Share on other sites More sharing options...
Marcia Selsor Posted January 15, 2014 Report Share Posted January 15, 2014 High Bridge is located in the UK. But he should be able to find a supplier there who will give him the COE information. Marcia Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted January 15, 2014 Author Report Share Posted January 15, 2014 Thanks for the replies, yes I can probably find out the COE of some of the clay I use. It is second hand clay from another potter who has no need to recycle but I will ask him sometime soon. Could be a good test Norm, thanks for the tip. Get a glaze and slowly change its COE to see what happens. I was just wondering if there was an easy way to work it out. I am assuming when you use the bar and props you are looking at starting width and then how far the clay pushes the props? Then some maths to give you the number. More research is needed on my part, I did snoop around digital fire trying to find an answer but it never appeared. Link to comment Share on other sites More sharing options...
Norm Stuart Posted January 15, 2014 Report Share Posted January 15, 2014 Ceramacists who own a COE measurement device in the US charge about $65 to provide a reading on a clay bar. In theory you could do this with kiln props, taking into account the COE of the shelf this is sitting on . . . But consider how small the measurement is. If you measure the expansion of a 30 cm bar over a range of 1,000 degrees C; Clay with a high COE of 8.0 x 10-6 meters per degree C will expand 2.4 mm; Clay with a low COE of 3.0 x 10-6 meters per degree C will expand 0.9 mm. That's enough expansion to make glass fit or crack, but way too small to measure with kiln furniture - assuming I'm capable of simple math, which my Third Grade teacher was skeptical of. So anyone with better math skills please feel free to critique this. Thanks for the replies, yes I can probably find out the COE of some of the clay I use. It is second hand clay from another potter who has no need to recycle but I will ask him sometime soon. Could be a good test Norm, thanks for the tip. Get a glaze and slowly change its COE to see what happens. I was just wondering if there was an easy way to work it out. I am assuming when you use the bar and props you are looking at starting width and then how far the clay pushes the props? Then some maths to give you the number. More research is needed on my part, I did snoop around digital fire trying to find an answer but it never appeared. Link to comment Share on other sites More sharing options...
Guest JBaymore Posted January 15, 2014 Report Share Posted January 15, 2014 The numbers are such that a dilatometer is really the tool of choice. The second method is the "varying expansion glazes" method. Wanna' pick one up? http://www.ortonceramic.com/shop/category.aspx/dilatometers/32/ best, ................john Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted February 17, 2014 Author Report Share Posted February 17, 2014 Couldn't seem to find the thread I was going to post this in. Not sure what happened to it. Anyway. A interesting document on thermal expansion and glaze fit worth a read if you are into that kind of thing. http://studiopotter.org/pdfs/sp28_1_sohngen.pdf Link to comment Share on other sites More sharing options...
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